Voltage-gated Cav1.4 Ca2+ channels are highly localized in the synaptic terminals of rod and cone photoreceptors. Ca2+ influx through these channels triggers the release of glutamate, which initiates the transmission of visual information through the retinal circuitry and into the brain. Mutations in Cav1.4 cause several visual impairments including congenital stationary night blindness type 2 (CSNB2), cone-rod dystrophy (CRD), and X-linked retinal disorder. These channelopathies illustrate the importance of Cav1.4 for normal vision, as well as the need to understand how Cav1.4 channels are regulated. In contrast to our knowledge of other Cav1 channels, little is known about the factors that influence Cav1.4 function. Therefore, it is important to understand how altered Cav1.4 function causes visual impairments. In this proposal, I will address the importance of an alternatively spliced exon (exon 47) in the Cav1.4 distal C-terminal regulatory domain (DCRD); that is known to regulate channel activation and inactivation, by interacting with regions in the proximal C-terminal regulatory domain (PCRD). This will be accomplished by determining the functional and structural significance of exon 47 on Cav1.4 activation and inactivation in HEK 293T cells, using electrophysiological and biochemical methods (aim 1), and by characterizing the expression of the Cav1.4 splice variant in human retina, using quantitative RT-PCR and in situ hybridization (aim 2).